Coronary calcification by electron beam computed tomography and obstructive coronary artery disease: a model for costs and effectiveness of diagnosis as compared with conventional cardiac testing methods.

OBJECTIVES The purpose of this study was to determine if electron beam computed tomography (EBCT) has potential as a cost-effective approach to diagnosis of obstructive coronary disease. BACKGROUND Coronary calcification quantified by EBCT is closely related to the extent of atherosclerosis. METHODS A model based upon published sensitivities (Se)/specificities (Sp) for diagnosis in an ambulatory patient of obstructive coronary disease (> or =50% stenosis) and population prevalence was tested for angiography alone, or treadmill exercise, stress echocardiography, stress thallium or predetermined EBCT calcium score outpoints, followed by angiography if indicated. RESULTS Total direct testing costs increased in proportion to disease prevalence whereas cost-effectiveness, direct costs/patient diagnosed correctly with disease, decreased as a function of prevalence. Using an EBCT calcium score of 168 (Se/Sp = 71%/90%) provided for the least costly and most cost-effective noninvasive pathway. Calcium scores of 80 (Se/Sp = 84%/84%) and 37 (Se/Sp = 90%/77%) were also cost-effective when prevalence of disease was < or =70%; but results for a >0 calcium score (Se/Sp = 95%/46%) cutpoint were not superior to conventional methods. Calcium score cutpoints of 37, 80 or 168 provided similar or superior overall negative and positive predictive values to conventional noninvasive testing pathways across all prevalence subgroups. CONCLUSIONS In ambulatory patients evaluated for obstructive coronary disease, a testing pathway utilizing quantification of coronary calcium by EBCT as an initial noninvasive testing approach minimized direct costs, and maximized cost-effectiveness in population groups with low/ moderate disease prevalence (< or =70%); as expected, direct angiography as the first and only test proved most cost-effective in patients with a high prevalence (>70%) of disease.